Epoxy resin composition

ABSTRACT

A composition comprising (A) an epoxide containing at least two epoxy groups per molecule, (B) a polyol containing at least two hydroxy groups per molecule or a primary or secondary amine containing at least two amino-hydrogen atoms per molecule, and (C) a solid compound containing at least two isocyanate groups, exhibits high storage stability and is useful as protective coating or adhesive.

This invention relates to an epoxy resin composition containing twocuring agents having different reactivities, a method for themanufacture of a one-component thermosetting resin composition, the useof said one-component thermosetting resin composition as protectivecoating or adhesive and the crosslinked products obtainable by curingsaid one-component thermosetting resin composition.

Industry continues to seek new materials which can be prepared in asimple manner, which are shelf stable, uncomplicated in use and provideever increasing greater variety of readily tailorable properties.

Because of their versatility and variety, epoxy based systems areimportant basic resins for adhesives and composites and are most usefulin many areas of applications (aero, automotive, industrial, consumeretc.).

The principal reaction undergone by epoxy systems is of the additiontype (catalysed or not) with amines, acids, anhydrides etc. Theformulation can be of the single component type (involving stabilisedmixtures of the epoxy resin and the hardener) or double component type(in which the reactant is mixed with the epoxy resin just prior to use).The single component type is simpler to use with less packaging waste;however, great care needs to be taken to ensure that pre-mature reactiondoes not occur resulting in poor shelf life before use. Conventional hotmelt and heat curable powder epoxy resin compositions, which can beprepared from an epoxy resin and a hardener composition containing anamine solidifying system and a latent hardener, are disclosed in U.S.Pat. No. 5,708,120, WO 97/19124 and WO 97/19125.

Isocyanates are also of considerable interest due to their ability toundergo rapid nucleophilic addition reactions with hydroxy groups, aminogroups and other active hydrogen containing groups, thus producingurethane and urea products. In order to use isocyanates in singlecomponent systems it is well known, for instance from U.S. Pat. No.4,483,974, to produce stabilised/deactivated isocyanate dispersions orpowders having a shell of urea or urethane. U.S. Pat. No. 4,067,843describes the preparation of granular phenolicurethane compounds from analready co-polymerised mixture of polyisocyanates and hydroxy-terminatedpolydienes. These granules are useful as thermoset adhesives.

Conventional epoxy systems containing amines or anhydrides as latentcuratives have the disadvantage that the final cure is carried out atrelatively high temperatures (180–220° C.).

It has now been found that mixtures of epoxy resins, polyamines orpolyols and solid isocyanates form highly tailorable, shelf stableone-component compositions which gel or solidify at ambient temperatureand can be completely cured at the temperature range of 60 to 180° C.

Accordingly, the present invention relates to a composition comprising

-   (A) an epoxide containing at least two epoxy groups per molecule,-   (B) a polyol containing at least two hydroxy groups per molecule or    a primary or secondary amine containing at least two amino-hydrogen    atoms per molecule, and-   (C) a solid compound containing at least two isocyanate groups.

Suitable as component (A) for the preparation of the compositionsaccording to the invention are the epoxy resins customarily employed inepoxy resin technology. Examples of epoxy resins are:

I) Polyglycidyl and poly(β-methylglycidyl) esters, obtainable byreaction of a compound having at least two carboxy groups in themolecule with epichlorohydrin or β-methyl-epichlorohydrin, respectively.The reaction is advantageously carried out in the presence to bases.

As compounds having at least two carboxy groups in the molecule theremay be used aliphatic polycarboxylic acids. Examples of suchpolycarboxylic acids are oxalic acid, succinic acid, glutaric acid,adipic acid, pimelic acid, suberic acid, azelaic acid and dimerised ortrimerised linoleic acid.

It is also possible, however, to use cycloaliphatic polycarboxylicacids, for example tetrahydrophthalic acid, 4-methyltetrahydrophthalicacid, hexahydrophthalic acid and 4-methyl-hexahydrophthalic acid.

Aromatic polycarboxylic acids may also be used, for example phthalicacid, isophthalic acid and terephthalic acid.

II) Polyglycidyl or poly(β-methylglycidyl) ethers, obtainable byreaction of a compound having at least two free alcoholic hydroxy groupsand/or phenolic hydroxy groups with epichlorohydrin orβ-methylepichlorohydrin, respectively, under alkaline conditions or inthe presence of an acid catalyst with subsequent alkaline treatment.

Such glycidyl ethers are derived, for example, from acyclic alcohols,e.g. from ethylene glycol, diethylene glycol or higher poly(oxyethylene)glycols, propane-1,2-diol or poly-(oxypropylene) glycols,propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene) glycols,pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol,1,1,1-trimethylolpropane, pentaerythritol, sorbitol, and also frompolyepichlorohydrins.

Further such glycidyl ethers are derived from cycloaliphatic alcohols,such as 1,4-cyclo-hexanedimethanol, bis(4-hydroxycyclohexyl)methane or2,2-bis(4-hydroxycyclohexyl)-propane, or from alcohols containingaromatic groups and/or further functional groups, such asN,N-bis(2-hydroxyethyl)aniline orp,p′-bis(2-hydroxyethylamino)diphenylmethane.

The glycidyl ethers may be based on mononuclear phenols, for exampleresorcinol or hydroquinone, or on polynuclear phenols, for examplebis(4-hydroxyphenyl)methane, 4,4-dihydroxybiphenyl,bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane or2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.

Further suitable hydroxy compounds for the preparation of glycidylethers are novolaks, obtainable by condensation of aldehydes, such asformaldehyde, acetaldehyde, chloral or furfuraldehyde, with phenols orbisphenols unsubstituted or substituted by chlorine atoms or byC₁–C₉alkyl groups, for example phenol, 4-chlorophenol, 2-methylphenol or4-tert-butyl-phenol.

III) Poly(N-glycidyl) compounds, obtainable by dehydrochlorination ofthe reaction products of epichlorohydrin with amines that contain atleast two amine hydrogen atoms. Those amines are, for example, aniline,n-butylamine, bis(4-aminophenyl)methane, m-xylene-diamine orbis(4-methylaminophenyl)methane.

The poly(N-glycidyl) compounds, however, include also triglycidylisocyanurate, N,N′-di-glycidyl derivatives of cycloalkyleneureas, suchas ethyleneurea or 1,3-propyleneurea, and diglycidyl derivatives ofhydantoins, such as of 5,5-dimethylhydantoin.

IV) Poly(S-glycidyl) compounds, for example di-S-glycidyl derivatives,derived from dithiols. for example ethane-1,2-dithiol orbis(4-mercaptomethylphenyl) ether.

V) Cycloaliphatic epoxy resins, for example bis(2,3-epoxycyclopentyl)ether, 2,3-epoxycyclopentylglycidyl ether,1,2-bis(2,3-epoxycyclopentyloxy)ethane or3,4-epoxwyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate.

Alternatively, epoxy resins may be used in which the 1,2-epoxide groupsare bonded to different hetero atoms and/or functional groups; thosecompounds include, for example, the N,N,O-triglycidyl derivative of4-aminophenol, the glycidyl ether-glycidyl ester of salicylic acid,N-glycidyl-N′-(2-glycidyloxypropyl)-5,5-dimethylhydantoin and2-glycidyloxy-1,3-bis-(5.5-dimethyl-1-glycidylhydantoin-3-yl)propane.

For the preparation of the compositions according to the invention, itis preferred to use a diglycidyl ether or ester

Especially preferred as component (A) are a diglycidyl ether ofbisphenol A and a diglycidyl ether of bisphenol F.

Component (B) of the mixtures according to the invention can, asmentioned, be any polyol having at least two hydroxy groups or any aminehaving at least two amino-hydrogen atoms.

Suitable polyols are aliphatic and aromatic polyols.

Examples of suitable aliphatic polyols are ethylene glycol, diethyleneglycol, polyethylene glycol, propylene glycol, polypropylene glycol,propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol,hexane-1,2,3-triol, glycerine, 1,1,1-trimethylolpropane, pentaerythritoland sorbitol.

Suitable aromatic polyols are, for example, resorcinol, hydroquinone,N,N-bis-(2-hydroxyethyl)aniline,p,p-bis-(2-hydroxyethylamino)-diphenylmethane,bis-(4-hydroxyphenyl)-methane, 4,4′-dihydroxybiphenyl,bis-(4-hydroxyphenyl)-sulfone,1,1,2,2-tetrakis-(4-hydroxyphenyl)-ethane,2,2-bis-(4-hydroxyphenyl)-propane,2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane, phenol novolaks andcresol novolaks.

Amines as component (B) may be aliphatic, cycloaliphatic, aromatic andheterocyclic amines, such as bis-(4-aminophenyl)-methane,aniline/formaldehyde resins, benzylamine. n-octylamine,propane-1,3-diamine, 2,2-dimethyl-1,3-propanediamine,hexamethylenediamine diethylenetriamine, bis-(3-aminopropyl)-amine,N,N-bis-(3-aminopropyl)-methylamine, triethylenetetramine,tetraethylenepentamine, pentaethylenehexamine,2,2,4-trimethylhexane-1,6-diamine, m-xylenediamine, 1,2- and1,4-diaminocyclohexane, bis-(4-aminocyclohexyl)-methane,bis-(4-amino-3-methyl-cyclohexyl)-methane,2,2-bis-(4-aminocyclohexyl)-propane, piperazine,3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine),polyaminoimidazolines, polyaminoamides, polyoxyalkyleneamines (e.g.Jeffamines® made by Texaco), 1,1 4-diamino-4,11-dioxatetradecane,dipropylenetriamine 2-methyl-1,5-pentanediamine,N,N′-dicyclohexyl-1,6-hexanediam ine, N,N′-dimethyl-1,3-diaminopropane,N,N′-diethyl-1,3-diaminopropane, N,N-dimethyl-1,3-diaminopropane,secondary polyoxypropylene-diamines and -triamines,2,5-diamino-2,5-dimethylhexane. bis-(aminomethyl)-tricyclopentadiene,m-aminobenzylamine, 1,8-diamino-p-menthane,bis-(4-amino-3,5-dimethylcyclohexyl)-methane,1,3-bis-(aminomethyl)-cyclohexane, dipentylamine.bis-(4-amino-3,5-diethylphenyl)-methane, 3,5-diethyltoluene-2,4-diamineand 3,5-diethyltoluene-2,6-diamine.

The polyetheramines disclosed in U.S. Pat. No. 5,275,853 are alsosuitable as component (B) in the compositions according to theinvention.

Preferably, component B is an aliphatic or cycloaliphatic amine.

Cyclohexylamine, 4,4′-diaminodicyclohexylmethane,4,4′-diamino-3,3′-dimethyidicyclohexyl-methane,2,2-bis(4-aminocyclohexyl)propane are2,2-bis(4-amino-3-methylcyclohexyl)propane are particularly preferred.

Component C is an isocyanate group containing compound or a mixture ofisocyanate group containing compounds which is solid at roomtemperature. Preferably component C is applied in the form of a powder.

Polyisocyanates useful as component (C) in the compositions according tothe invention include low-viscosity aliphatic, cycloaliphatic oraromatic isocyanates and mixtures thereof

Preferably, component C is a diisocyanate monomer, a diisocyanate dimer,a diisocyanate trimer or a solid reaction product of a diisocyanate andan aliphatic diol.

Examples for suitable polyisocyanates are 2,4-diphenylmethanediisocyanate, 4,4-diphenylmethane diisocyanate, hexane-1,6-diisocyanate,cyclohexane-1,2-diisocyanate. cyclohexane-1,3-diisocyanate,cyclohexane-1,4-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate,isophorone diisocyanate, phenylenediisocyanate, xylene diisocyanate,toluene-2,4-diisocyanate, toluene-2,6-diisocyanate,naphthalene-1,4-diisocyanate, 4,4′-diphenylether diisocyanate,4,4′-diphenylsulfone diisocyanate, 2,2-bis(4-isocyanatophenyi)propaneand 3,3′,4,4′-diphenylmethane tetraisocyanate.

Polyol-modified polyisocyanates and mixtures of liquid polyisocyanateswith higher molecular polyisocyanates or carbodiimide polyisocyanatescan also be applied. Further suitable polyisocyanates are dimers andtrimers of the above-mentioned multivalent isocyanates; suchpolyisocyanates have end-position free isocyanate groups and contain oneor more uretdione and/or isocyanurate rings.

Particularly preferred polyisocyanates are 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 2,3-toluene diisocyanate, 3,4-toluenediisocyanate, 4,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethanediisocyanate, p-phenylene diisocyanate, isophorone diisocyanate and4,4′-methylene-bis(cyclohexylisocyanate).

In the curative compositions according to the invention the relativeamounts of components (A), (B) and (C) can vary within wide ranges.

Purposively, component (B) is applied in such an amount that per epoxygroup of component (A) from 0.05 to 0.60, preferably from 0.1 to 0.4,hydroxy groups or amine hydrogen atoms, respectively, are present.

The crosslinking density of the cured product can be adjusted by theamount of component (C). Preferably, the composition according to theinvention contains component (C) in such an amount that per epoxy groupof component (A) from 0.05 to 1.00. preferably from 0.1 to 0.5,isocyanate groups are present.

The compositions according to the invention may, where appropriate,comprise further accelerators, such as imidazoles orbenzyldimethylamine.

Moreover, the curable mixtures may comprise fillers, such as metalpowder, wood dust, glass powder, glass beads, semimetal oxides and metaloxides, for example SiO₂ (aerosils. quartz, quartz powder, fused silicapowder), corundum and titanium oxide, semimetal nitrides and metalnitrides, such as silicon nitride, boron nitride and aluminium nitride,semimetal carbides and metal carbides (SiC), metal carbonates (dolomite,Amine 21k, CaCO₃), metal sulfates.(barite, gypsum), mineral fillers andnatural or synthetic minerals mainly from the silicates series, such aszeolites (especially molecular sieves) talcum, mica, kaolin,wollastonite, bentonite and others.

In addition to the above-mentioned additives, the curable mixtures maycomprise further customary adjuvants, for example antioxidants, lightstabilizers, plasticizers, colorants, pigments, thixotropic agents,toughness improvers, antifoams, antistatics, glidants and demouldingauxiliaries.

The compositions according to the invention may be prepared by handmixing or by using known mixing apparatus, for example stirrers,kneaders or rollers. In the case of solid epoxy resins, dispersing maybe carried out also in the melt. The temperature during the dispersingis to be so selected that premature curing does not occur during themixing process. The optimum curing conditions are dependent on themicrogel, on the type and amount of the nitrogen-containing base, on theepoxy resin and on the form of dispersing, and can be determined by theperson skilled in the art in each case using known methods.

Due to the use of two hardeners of different reactivity, thecompositions according to the invention can be cured in a two-stepprocess. After mixing, the epoxy resin (A) reacts at room temperature orat slightly elevated temperature with the polyol or polyamine (B); theincrease of viscosity thereby specifies the extent of this so-calledB-stage curing.

The products obtained by the room temperature curing step generally showgood tack and exhibit excellent storage stability.

In the second curing step which requires higher temperatures (60–180°C.) the secondary hydroxy groups formed during the first curing stepreact with the isocyanate groups of component (C). The crosslinkedproducts obtained by this C-stage curing distinguish by an excellent lapshear strength.

The invention further relates to a method for the manufacture of aone-component thermosetting resin composition in gel, paste or powderform which comprises mixing components (A), (B) and (C) according toclaim 1 and reacting the mixture at temperatures <50° C. until theviscosity of the mixture is at least 10% higher than the initialviscosity.

The storage stable one-component resin compositions obtained by theB-stage curing are particularly useful as protective coatings oradhesives.

The invention further relates to the crosslinked products obtainable bycuring the one-component thermosetting resin composition at 60–180° C.

In the examples, which are illustrative of the present invention and aretherefore not intended as a limitation on the scope thereof, thefollowing. ingredients are used:

-   -   Epoxy resin 1: liquid bisphenol A diglycidylether having an        average epoxide equivalent of 5.395 equivalents/kg    -   Epoxy resin 2: liquid bisphenol F diglycidylether having an        average epoxide equivalent of 5.95 equivalents/kg    -   Amine 1: 4,4′-diamino-3,3′-dimethyl dicyclohexyl methane    -   Amine 2: cyclohexylamine    -   Amine 3: 4,7,10-trioxa-1, 13-tridecanediamine (trade name        Q19262)    -   Isocyanate 1: toluenediisocyanate uretidone dimer (trade name        Desmodur TT, NCO content ˜24% by weight)    -   Isocyanate 2: isophorone diisocyanate trimer (trade name        Vestanate, NCO content ˜17° by weight)

EXAMPLE 1 Comparison

100 g Epoxy resin 1 is blended with 6 g amine 1. The mixture isthoroughly hand-mixed and after 24 hours the mixture is a clear viscousliquid showing good tack and appears to be stable with time.

EXAMPLE 2

100 g epoxy resin 1 is hand-mixed with 6 g amine 1. Subsequently, 17.5 gisocyanate 1 powder is added and the mixture is passed through thetriple roll mill for two cycles. On standing for 24 hours, a whiteviscous liquid is obtained showing good tack and high storage stability.

EXAMPLE 3

A mixture of 100 g epoxy resin 1,6 g amine 1 and 14 g isocyanate 1powder is processed as described in Example 2. The product is a viscousliquid showing good tack and high storage stability.

EXAMPLE 4

A mixture of 100 g epoxy resin 1,6 g amine 1 and 10.5 g isocyanate 1powder is processed as described in Example 2. The product is a viscousliquid showing good tack and high storage stability.

EXAMPLE 5 Comparison

A blend of 100 g epoxy resin 1 and 8 g amine 1 is mixed thoroughly andallowed to stand for 24 hours. The resulting product is a highly viscousclear liquid which exhibits little tack.

EXAMPLE 6

A blend of 100 g epoxy resin 1, 8 g amine 1 and 23.4 g isocyanate 1powder is hand-mixed and passed through the triple roll mill for twocycles. The resulting product is a white, highly viscous liquidexhibiting no tack.

From the gelled products obtained in Examples 1–6, lap shear samples aremade by curing at 120° C. for 30 min using aluminium plates (L165) intriplicate. The results are summarised in Table 1.

TABLE 1 Example Lap Shear Strength [N/mm²] 1 0.02 2 12.07 3 10.97 410.48 5 0.64 6 16.55

The data show that the samples containing the latent isocyanatecrosslinker exhibit significant higher lap shear strength thancomparative examples 1 and 5.

EXAMPLES 7–14

Blends of epoxy resin 1, amine 1 and isocyanate 2 are prepared andprocessed as described in Example 2. The isocyanate 2 is supplied inpellet form and is put through a coffee grinder (white powder, irregularin shape, average particle diameter approximately 100 μm).The resultingproducts are milky viscous pastes.

From the gelled products obtained in Examples 7–14, lap shear samplesare made by curing at 60° C. and 80° C., respectively, for 16 h usingaluminium plates (L165) in triplicate. The results are summarised inTable 2.

TABLE 2 Example 7 8 9 10 11 12 13 14 epoxy resin 1 [g] 100 100 100 100100 100 100 100 HY 2954 [g] 6 6 6 6 8 8 8 8 isocyanate 2 [g] 8.93 13.4617.93 22.40 11.93 17.93 23.93 29.93 Lap Shear Strength [N/mm²] 16 h/60°C. 3.55 2.74 1.74 0.42 3.67 4.02 4.81 4.97 16 h/80° C. 6.47 6.17 6.011.95 3.32 5.23 4.99 5.29

EXAMPLE 15 Comparison

A mixture of 100 g epoxy resin 1 and 5.87 g amine 3 is prepared andprocessed as described in Example 1. The resulting product is a clearviscous liquid. Lap shear samples made with this composition and curedat 60° C. and 80° C., respectively, do not produce results as thesamples are still wet and tacky.

EXAMPLE 16

A mixture of 100 g epoxy resin 1, 5.87 g amine 3 and 18.6 g isocyanate 1powder is prepared and processed as described in Example 2. Theresulting product is a white viscous liquid.

Lap shear data of samples obtained from curing this composition aregiven in Table 3.

TABLE 3 Curing Conditions Lap Shear Strength [N/mm²] 4 h/60° C. 0.037 16h/60° C.  0.728 1 h/80° C. 1.64 2 h/80° C. 1.57 3 h/80° C. 2.90 4 h/80°C. 3.32 16 h/80° C.  4.41

The composition of Example 10 is cured at different temperatures for 30min and the following lap shear values are obtained:

TABLE 4 Curing Temperature Lap Shear Strength [N/mm²]  60° C. —  80° C.1.10 100° C. 2.28 120° C. 2.67 140° C. 2.85 160° C. 2.93 180° C. 3.39

EXAMPLE 17 Comparison

A mixture of 50 g epoxy resin 1, 50 g epoxy resin 2 and 6.73 9 amine 1is prepared and processed as described in Example 1. The resultingproduct is a clear viscous liquid. No lap shear values can be measuredwith samples cured 16 h at 60° C. and 80° C., respectively do notproduce results as the samples are still wet and tacky.

EXAMPLE 18

A mixture of 50 g epoxy resin 1, 50 g epoxy resin 2, 6.73 g amine 1 and19.7 g isocyanate 1 powder is prepared and processed as described inExample 2. The resulting product is a white viscous liquid. Lap sheardata of the cured products are summarized in Table 5.

TABLE 5 Curing Lap Shear Strength Curing Lap Shear Strength Conditions[N/mm²] Conditions [N/mm²] 1 h/60° C. 5.18 30 min/60° C.  1.57 2 h/60°C. 7.64 30 min/80° C.  9.59 3 h/60° C. 8.12 30 min/100° C. 10.85 4 h/60°C. 8.86 30 min/120° C. 10.59 16 h/60° C.  11.19 30 min/140° C. 8.29 1h/80° C. 10.13 30 min/160° C. 5.82 2 h/80° C. 12.31 30 min/180° C. 2.823 h/80° C. 12.58 4 h/80° C. 12.97 16 h/80° C.  13.59

EXAMPLES 19–27

Blends of epoxy resin 1, amine 1, amine 2 and isocyanate 1 are preparedand processed as described in Example 2. The resulting products aresolid; 19 is clear while 20–27 are white. The examples are cured at 60,and 80 and 120° C. for 1 h and the following lap shear data areobtained:

TABLE 6 Example 19 20 21 22 23 24 25 26 27 epoxy resin 1 [g] 100 100 100100 100 100 100 100 100 amine 1 [g] 10.6 10.6 10.6 10.6 10.6 10.6 10.610.6 10.6 amine 2 [g] 6 6 6 6 6 6 6 6 6 isocyanate 1 [g] 0 5.2 10.4 15.620.8 25.4 31.2 41.6 52.0 Lap Shear Strength [N/mm²] 1 h/60° C. 0.49 0.570.62 — 0.50 — 0.41 0.24 0.60 1 h/80° C. 0.29 0.55 0.63 — 0.80 — 1.270.94 1.18 1 h/120° C. 0.55 1.33 1.19 2.60 3.27 2.31 1.57

1. A method for the manufacture of a one-component thermosetting resincomposition in gel, paste or powder form which comprises mixing (A) anepoxide containing at least two epoxy groups per molecule, (B) analiphatic or cycloaliphatic primary or secondary amine containing atleast two amino-hydrogen atoms per molecule, and (C) a solid compoundcontaining at least two isocyanate groups, and reacting the mixture attemperatures <50° C. until the viscosity of the mixture is at least 10%higher than the initial viscosity.
 2. The method of claim 1 whereincomponent (A) is a diglycidyl ether or a diglycidyl ester.
 3. The methodof claim 1 wherein component (A) is a diglycidyl ether of bisphenol A orbisphenol F.
 4. The method of claim 1 wherein component (B) is acyclohexylamine, 4,4′diaminodicyclohexylmethane,4,4′-diamino-3,3′-dimethyldicyclohexylmethane,2,2-bis(4-aminocyclohexyl)propane or2,2-bis(4-amino-3-methylcyclohexyl)propane.
 5. The method of claim 1wherein component C is a diisocyanate monomer, a diisocyanate dimer, adiisocyanate trimer or a solid reaction product of a diisocyanate and analiphatic diol.
 6. The method of claim 5 wherein the diisocyanate isselected from the group consisting of 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 2,3-toluene diisocyanate, 3,4-toluenediisocyanate, 4,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethanediisocyanate, p-phenylene diisocyanate, isophorone diisocyanate and4,4′-methylene-bis (cyclohexylisocyanate).
 7. A crosslinked productobtained by curing the one-component thermosetting resin compositionobtained by the process according to claim 1 at 60–180° C.